The PCT documents SE 2012 050 319 and SE 2013/051 059 (assigned to Climeon AB) disclose a novel thermodynamic cycle using CO2 gas as working fluid and alkaline liquids (amines) as temporary and reversible CO2 absorbents. CO2 is liberated from CO2-saturated amines in the hot section (e.g. 90° C.), generating 1-10 bar pressure, and, following expansion through a turbine, absorbed by non-saturated amine in the cold section of the process. The steady-state pressure in the cold section is significantly below atmospheric pressure such that pressure ratios between the hot and cold side of the process between 25 and 4 can be realized. Variations and improvements are disclosed in SE 1300 576-4, SE 1400 027-7 and SE 1400 160-6, all assigned to Climeon, hereby incorporated by reference.
General background relating to expansion machines is found in the following disclosures and references:
Moustapha, Zelesky, Baines & Japikse, “Axial and radial turbines”, Concepts NREC, 2003, ISBN 0-933283, see especially FIG. 8.19. Japikse & Baines, “Introduction to turbomachinery”. Balje O., “Turbomachines—A Guide to Design Selection and Theory”, 1981, ISBN 0-471-06036-4.
Among patent disclosures, EP 2 669 473 (Mitsubishi, 2012) and US 2013/0280 036 (Honeywell) are recent examples of technological progress in the construction of radial turbines. U.S. Pat. No. 5,408,747 (United Technologies Corp., 1994) describes a CFD approach to the design of radial-inflow turbines.
Regarding the removal of condensing liquids from the turbine during the expansion, the following disclosures are of general interest: EP 2092 165 by ABB (2007), EP 2128 386 by Siemens (2008), EP 1925 785 by Siemens (2006), EP 1103 699 by Mitsubishi (2007), EP 0812 378 by Joel H. Rosenblatt (1995). The latter publication discloses the management of two-phase systems such as ammonia-water in multi-stage turbines. This invention differs from the a.m. disclosures in the sense that one-stage radial turbines are employed which pose very different challenges compared to axial turbines.
For the invention, it is relevant to appreciate that expansion machines can be selected on the basis of the Cordier/Balje diagram of dimensionless parameters including the rotation frequency, average volume flow and the isentropic heat drop. Comparing axial and radial turbines, the optimum performance range of axial turbines as function of the dimensionless specific speed is rather broad. By contrast, radial turbines have a rather narrow range where the turbine efficiency is above 80, or >85 or >88% of theoretical maximum. Provided the dimensionless specific speed is about 0.7 (range 0.5-0.9), a single stage radial turbine can be as efficient as a one- or two-stage axial turbine (see Balje).